1. Technical Field
The present invention relates to a contact contacting structure between a pair of contacts respectively for hot-line connection with electric circuits, and more particularly, to a contact contacting structure in which high electric energy is generated between a pair of contacts that contacts with or separates from each other.
2. Related Art
An electric connector used for hot-line connection of electric power lines and the like for transmitting high voltage, high-current electric power causes an arc discharge between a pair of adjacent contacts when the other connector to which the electric connector is connected is inserted or removed, due to high electric energy that has been accumulated between the close contacts. Such arc discharge is also caused by induced electromotive force resulting from the removal of one connector connected to an inductive load from the other connector connected to the power line.
The arc discharge hastens deterioration of the electric connector such as erosion of the contacts. The problem has been addressed by largely two methods. According to the first method disclosed in JP-A-2010-56055 (Patent Literature 1), a permanent magnet or the like is disposed in the direction orthogonal to the direction of opposition between the pair of contacts to generate a magnetic field and deflect the direction of the arc by Lorentz force, thereby preventing damage to the contacts due to the arc discharge.
According to the second method, the electric energy accumulated between the pair of contacts is decreased to prevent the occurrence of arc discharge. The electric energy accumulated in the pair of contacts is in proportion to the voltage and current between the pair of contacts. Accordingly, JP-A-63-86281 (Patent Literature 2) and JP-UM-A-4-2467 (Patent Literature 3) describe techniques for lowering the voltage between the pair of contacts at the time of separation from each other to prevent the occurrence of arc discharge.
Specifically, in a contact contacting structure 100 described in Patent Literature 2 as illustrated in FIG. 6, a contact 101 and a resistor 102 with a higher electric resistivity ρ than that of the contact 101 are disposed continuously along a movement path in which a contact 103 of the counterpart connector moves, and when the other contact 103 is drawn out and separated from the movement path, the contact 103 is separated at a leading end 102a of the resistor 102 with the highest resistance value to keep the voltage between the two contacts resulting in no arch discharge, thereby preventing the occurrence of arc discharge.
In a contact contacting structure 110 described in Patent Literature 3, as illustrated in FIGS. 7A and 7B, the resistance value of a contact 112 is more increased as a counterpart contact 114 moves in a separating direction (the rightward direction in the drawings) along a movement path in which the counterpart contacts 114 moves. While the counterpart contact 114 is fully inserted as illustrated in FIG. 7A, when the counterpart contact 114 is drawn from the movement path as illustrated in FIG. 7B, a large potential drop is caused in the contact 112 such that a leading end 112a of the contact 112 to which the contact 114 is adjacent has the highest resistance, and the voltage between the leading end 112a and the contact 114 does not cause arc discharge.
According to the first method described in Patent Literature 1, a permanent magnet or the like is disposed in the direction orthogonal to the direction of the opposition between the pair of contacts to generate a magnetic field. Accordingly, the contact contacting structure is complicated and large-sized. In addition, the structure does not prevent the occurrence of arc discharge, and electromagnetic noise resulting from arc discharge would exert an adverse effect on an electronic circuit such as a load. Therefore, the first method does not constitute a substantive solution.
In the contact contacting structure 100 according to the second method, when being drawn out, the other contact 103 is separated from the contact 101 via the resistor 102 with high electric resistivity ρ, and the voltage at the leading end 102a of the resistor 102 drops due to the resistance value of the resistor 102. Since the resistance value of the resistor 102 is in proportion to the distance from a connection position ×0 relative to the contact 101, the resistance value of the resistor 102 is largest at a position ×1 of the leading end 102a of the resistor 102. However, even though the resistance value of the resistor 102 is largest at the leading end 102a of the resistor 102, the potential may not be sufficiently dropped by the resistor 102 depending on the voltage applied between the contacts 101 and 103 and the current flowing between the contacts 101 and 103, thereby leading to the occurrence of arc discharge.
In this case, the resistor 102 may be formed from a conductive material with a still higher electric resistivity ρ. However, if the resistor 102 with a higher resistance value is used, when the contact position of the contact 103 of the counterpart connector moves from the contact 101 to the resistor 102, the resistor 102 constitutes an insulator like the air to generate arc discharge by electric energy between the adjacent contacts 101 and 103. Therefore, the resistance value of the resistor 102 cannot be raised substantially until the contact position of the contact 103 comes at a predetermined distance from the connection position ×0, and the problem cannot be solved by the change of the conductive material.
Accordingly, the resistance value of the leading end 102a may be increased by extending the distance from the connection position ×0 to the leading end position ×1 of the resistor 102. However, the resistance value increases simply in proportion to the distance along the separating direction, and there is an upper limit to the resistance value of the resistor 102. The extension in the separating direction results in the larger size of the contact contacting structure.
In the contact contacting structure 110 described in Patent Literature 3, the resistance value is more increased as the contact 102 moves in the separating direction (the rightward direction in FIGS. 7A and 7B) along the movement path. The electric resistivity ρ of the conductive material for use in the contact 102 takes a value specific to each conductive material. Accordingly, in order to increase the resistance value per unit length along with the movement in the separating direction (the rightward direction in FIGS. 7A and 7B), it is necessary to prepare and arrange successively many kinds of conductive materials gradually larger in electric resistivity ρ in the separating direction. This method is not practical due to difficulty of manufacture.